/Engine/Source/Runtime/Engine/Classes/Kismet/KismetSystemLibrary.h
Prints a string to the log If Print To Log is true, it will be visible in the Output Log window. Otherwise it will be logged only as 'Verbose', so it generally won't show up.
static void LogString ( const [FString](API\Runtime\Core\Containers\FString) & InString, bool bPrintToLog )